1. Field of the Invention
This invention is directed to methods for treating endoleaks arising from endovascular repair of abdominal aortic aneurysms. Specifically, the methods of this invention involve the in situ sealing of endoleaks after placement of an endovascular prostheses in the abdominal aorta. Sealing of endoleaks is achieved by injection of a biocompatible fluid composition at the site of the endoleak which composition in situ solidifies and adheres to the vascular and/or prosthetic wall to seal the leak. Preferably, the biocompatible fluid composition comprises a contrast agent to allow the clinician to visualize the sealing process.
2. References
The following publications, patent applications and patents are cited in this application as superscript numbers:
1 May, et al., xe2x80x9cConcurrent Comparison of Endoluminal Versus Open Repair in the Treatment of Abdominal Aortic Aneurysms: Analysis of 303 Patients by Life Table Methodxe2x80x9d, J. Vasc. Surg. 27(2):213-221 (1998)
2 White, et al., J. Endovasc. Surg., 3:124-125 (1996)
3 Marty, et al., xe2x80x9cEndoleak After Endovascular Graft Repair of Experimental Aortic Aneurysms: Does Coil Embolization with Angiographic xe2x80x9cSealxe2x80x9d Lower Intraaneursymal Pressurexe2x80x9d, J. Vasc. Surg., 22(3):454-462 (1998)
4 Money, et al., xe2x80x9cPerioperative Charge Comparison and Endovascular Abdominal Aortic Aneurysm Repairxe2x80x9d, JPV 1.1-1.2, Presented at the 6th Annual Symposium on Current Issues and New Techniques in Interventional Radiology at New York, New York in November, 1998
5 Beebe, et al., xe2x80x9cCurrent Status of the United States Vanguard(trademark) Endograft Trialxe2x80x9d, JPVA 2.1-2.3, Presented at the 6th Annual Symposium on Current Issues and New Techniques in Interventional Radiology at New York, New York in November, 1998
6 Hopkinson, et al., xe2x80x9cCurrent Critical Problems, New Horizons and Techniques in Vascular and Endovascular Surgeryxe2x80x9d, JPIII 4.1-4.2, Presented at the 6th Annual Symposium on Current Issues and New Techniques in Interventional Radiology at New York, New York in November, 1998
7 Kinugasa, et al., xe2x80x9cDirect Thrombosis of Aneurysms with Cellulose Acetate Polymerxe2x80x9d, J. Neurosurg., 77:501-507 (1992)
8 Greff, et al., U.S. Pat. No. 5,667,767 for xe2x80x9cNovel Compositions for Use in Embolizing Blood Vesselsxe2x80x9d, issued Sep. 16, 1997
9 Greff, et al., U.S. Pat. No. 5,580,568 for xe2x80x9cCellulose Diacetate Compositions for Use in Embolizing Blood Vesselsxe2x80x9d, issued Dec. 3, 1996
10 Kinugasa, et al., xe2x80x9cEarly Treatment of Subarachnoid Hemorrhage After Preventing Rerupture of an Aneurysmxe2x80x9d, J. Neurosurg., 83:34-41 (1995)
11 Kinugasa, et al., xe2x80x9cProphylactic Thrombosis to Prevent New Bleeding and to Delay Aneurysm Surgeryxe2x80x9d, Neurosurg., 36:661 (1995)
12 Taki, et al., xe2x80x9cSelection and Combination of Various Endovascular Techniques in the Treatment of Giant Aneurysmsxe2x80x9d, J. Neurosurg., 77:37-42 (1992)
13 Evans, et al., U.S. patent application Ser. No. 08/802,252 for xe2x80x9cNovel Compositions for Use in Embolizing Blood Vesselsxe2x80x9d, filed Feb. 19, 1997.
14 Castaneda-Zuniga, et al., Interventional Radiology, in Vascular Embolotherapy, Part 1, 1:9-32, Williams and Wilkins, Publishers (1992)
15 Rabinowitz, et al., U.S. Pat. No. 3,527,224, for xe2x80x9cMethod of Surgically Bonding Tissue Togetherxe2x80x9d, issued Sep. 8, 1970
16 Hawkins, et al., U.S. Pat. No. 3,591,676, for xe2x80x9cSurgical Adhesive Compositionsxe2x80x9d, issued Jul. 6, 1971
17 Parodi, xe2x80x9cEndovascular AAA Stent Grafts: Technology, Training and Proper Patient Selection, JPVA 1.1-1.2 Presented at the 6th Annual Symposium on Current Issues and New Techniques in Interventional Radiology at New York, New York in November, 1998
18 van Schie, et al., xe2x80x9cSuccessful Embolization of Persistent Endoleak from a Patent Inferior Mesenteric Arteryxe2x80x9d, J. Endovasc. Surg., 4:312-315 (1997)
19 Walker, et al., xe2x80x9cA Study of the Patency of the Inferior Mesenteric and Lumbar Arteries in the Incidence of Endoleak Following Endovascular Repair of Infra-renal Aortic Eneurysmsxe2x80x9d, Clinical Radiology, 53:593-595 (1998)
All of the above publications, patent applications and patents are herein incorporated by reference in their entirety to the same extent as if each individual publication, patent application or patent was specifically and individually indicated to be incorporated by reference in its entirety.
Abdominal aortic aneurysms (AAA) represents a serious medical challenge and, when left untreated, eventual rupture of the aneurysm has significant morbidity associated therewith. When feasible, open surgery to repair the aortic aneurysm has been shown to be clinically successful.1 However, open surgery is often not feasible especially in patients suffering from severe cardiac disease, renal disease or other conditions which contraindicate open surgery. For example, conventional exposure of the infrarenal aorta necessitates a large abdominal incision, mobilization of the abdominal viscera, and retroperitoneal dissection which are associated with complications such as renal failure, pseudoaneurysms and bleeding. Infrarenal aortic clamping is also associated with an increased cardiac demand including an increase in left ventricular end diastolic volume and may be related to cardiac mortality.
Less invasive methods for treating abdominal aortic aneurysms avoid many of these problems and additionally result in reduced patient discomfort, reduced hospital stays and reduced care intensity.5 Endovascular grafts have ERG been investigated as one example of a less invasive method for the treatment of aneurysmal aortic disease. When compared to open surgery, endovascular grafting provides similar perioperative mortality rates notwithstanding the fact that endovascular grafting is often performed with individuals who are not candidates for open surgery due to one or more medical conditions which preclude such surgery.1,4 One of the main concerns regarding endovascular grafting is the continued blood flow into the aneurysm after grafting which blood flow is termed in the art as an endoleak.2 Endoleaks have been reported in from about 7 to about 37% of endovascular aortic aneurysm repairs3 with some reports placing this number as high as 44%.
Specifically, endovascular grafting requires catheter placement of an endovascular prosthesis at the abdominal aortic aneurysm site. Endoleaks arising after such grafting may be caused by incomplete sealing between the endovascular prosthesis and the aortic wall or by defects within the endovascular prosthesis. In addition, back blending from patent lumbar and inferior mesenteric arteries following placement of the endovascular prostheses in the aorta has also been recited as a potential cause of endoleaks.6 There is uniform agreement that large endoleaks that lead to aneurysm enlargement necessitate treatment in order to prevent aneurysm rupture. It is also reported that the size of the endoleak does not appear to be a relevant factor for pressure transmission into the aneurysm.3 
There are a variety of prophylactic and therapeutic treatment regimens for endoleaks reported in the literature. Prophylactic methods of inhibiting endoleaks by embolizing vasculature leading to the aneurysm, evidently with metallic coils, have been suggested and dismissed in an article by Walker, et al.19 Therapeutic methods for endovascular repair include placement of additional stents within the prosthesis; insertion of metallic coils into the aneurysm space to induce thrombosis therein; and embolization of the inferior mesenteric artery using a prepolymer/water soluble contrast agent compositions.18 
The goal of such treatments is complete exclusion of the aneurysm from systemic blood flow. While complete exclusion is desirable, secondary goal is to reduce intraaneursymal pressure (IAP) from blood flow into the aneurysm to acceptable levels thereby inhibiting the likelihood of rupture. In cases where no endoleaks arose after endovascular grafting, the mean IAP has been reported to be reduced by about 65%. However, when endoleaks arise, it is reported that the mean LAP, while initially decreasing significantly, stabilized after a week at a reduction of only 22%. Moreover, the use of coils to induce thrombosis and thereby reduce IAP did not have any significant impact on the LAP.
In view of existing problems associated with endovascular repair of endoleaks, the accepted treatment for these endoleaks is open surgery. However, the mortality rates for open surgery of endoleaks is higher than either initial open surgery for the abdominal aortic aneurysm or for the initial endovascular repair of the aneurysm.
In view of the above, reliable endovascular methods to inhibit endoleaks after endovascular graft repair of abdominal aortic aneurysms is desirable.
This invention is directed to methods for treating endoleaks arising from endovascular repair of abdominal aortic aneurysms. These methods provide for delivery of a fluid composition to the sites of endoleaks in the abdominal aorta which fluid composition, in situ, forms a coherent solid mass which adheres to vascular and/or prosthetic wall to seal the endoleak.
In a preferred embodiment, the fluid composition comprises a biocompatible polymer, a biocompatible solvent and a contrast agent to allow the clinician to visualize the procedure. In a further preferred embodiment, the contrast agent is a water insoluble contrast agent characterized by having an average particle size of about 10 xcexcm or less.
In another preferred embodiment, the fluid composition comprises a biocompatible prepolymer and a contrast agent which, again, is employed to allow the clinician to visualize the procedure. In a further preferred embodiment, the contrast agent is a water insoluble contrast agent characterized by having an average particle size of about 10 xcexcm or less.
Accordingly, in one of its method aspects, this invention provides a method for sealing endoleaks in a patient arising from endovascular repair of abdominal aortic aneurysms which method comprises:
identifying an abdominal aortic aneurysm in a patient;
endovascularly repairing said aneurysm by catheter delivery of an endovascular prosthesis to the site of said aneurysm thereby inhibiting blood flow into the aneurysm;
identifying one or more endoleaks in said patient; and
delivering to the site or sites of the endoleak in said patient a sufficient amount of a fluid composition comprising a biocompatible solvent and a biocompatible polymer under conditions wherein the fluid composition forms a coherent adhesive mass in situ at said site or sites thereby sealing the endoleaks.
In one preferred embodiment, the fluid composition further comprises a contrast agent to permit the clinician to detect the composition in vivo. The contrast agent can be either water soluble or water insoluble and preferably is water insoluble.
In another preferred embodiment, the fluid composition is delivered by a microcatheter, by a needle or any other access device.
Methods further comprising the step of delivering a detectable agent, such as a contrast agent, through the catheter or needle after it has been inserted into the artery and detecting the agent to confirm that the catheter has the proper placement prior to delivery of the fluid composition to the site of the endoleak are also provided.
In another of its method aspects, this invention is directed to a method for treating abdominal aortic aneurysms in a patient which method comprises:
identifying an abdominal aortic aneurysm in a patient;
endovascularly repairing said aneurysm by catheter delivery of an endovascular prosthesis to the site of said aneurysm thereby inhibiting blood flow into the aneurysm;
identifying the presence of one or more endoleaks in said patient;
delivering to the site or sites of endoleaks in said patient a sufficient amount of a fluid composition comprising a biocompatible prepolymer and a water insoluble contrast agent under conditions wherein the fluid composition forms a coherent mass in situ which adheres to the walls of the vascular site and/or prosthesis thereby sealing the endoleaks.
In a preferred embodiment, the fluid composition is delivered by either a microcatheter or by a needle.
This invention is also directed to kits of parts for use in endovascular treatment of aneurysms in a patient including sealing of endoleaks arising from such repair. In one embodiment, this kit comprises the following components:
(a) a fluid composition which is selected from the group consisting of (i) a biocompatible polymer and a biocompatible solvent and (ii) a biocompatible prepolymer and a water insoluble contrast agent which fluid composition forms a coherent mass in the presence of blood which mass adheres to the vascular surface and/or the surface of the endovascular prosthesis;
(b) a catheter suitable for delivering the fluid composition to an endoleak site formed from endovascular repair of an aneurysm; and
(c) a catheter suitable for delivering an endovascular prosthesis to the aneurysm.
In a preferred embodiment, this kit further comprises an endovascular prosthesis.
In another embodiment, this kit comprises the following components:
(a) a fluid composition which is selected from the group consisting of (i) a biocompatible polymer and a biocompatible solvent and (ii) a biocompatible prepolymer and a water insoluble contrast agent which fluid composition forms a coherent mass in the presence of blood which mass adheres to the vascular surface and/or the surface of the endovascular prosthesis;
(b) a catheter suitable for delivering the fluid composition to an endoleak site formed from endovascular repair of an aneurysm; and
(c) an endovascular prosthesis.
In a preferred embodiment, this kit further comprises a catheter suitable for delivering an endovascular prosthesis to the aneurysm.
This invention is directed, in part, to novel methods for sealing endoleaks in a patient which methods deliver endovascularly a fluid composition to the site of the endoleak which composition solidifies in situ to seal the endoleak. Specifically, the fluid compositions used herein provide for formation of a coherent adhesive mass which forms in situ thereby sealing endoleaks thereby overcoming complications heretofore associated with such leaks.
However, prior to discussing this invention in further detail, the following terms will first be defined:
The term xe2x80x9csealing an endoleakxe2x80x9d refers to a process wherein a fluid composition is injected at the site of the endoleak arising, for example, at or adjacent the site of an abdominal aortic aneurysm treated with an endovascular prosthesis. After delivery, the fluid composition solidifies in situ to seal the endoleak. Any endoleak can be treated in the methods of this invention including endoleaks arising, for example, from incomplete sealing between the endovascular prosthesis and the aortic wall, from defects within the endovascular prosthesis as described below, and/or from retrograde flow from patent lumbar and inferior mesenteric arteries following placement of the endovascular prosthesis in the aorta.
The term xe2x80x9cbiocompatible polymerxe2x80x9d refers to polymers which, in the amounts employed, are non-toxic, chemically inert, and substantially non-immunogenic when used internally in the patient and which, while soluble in the biocompatible solvent, are substantially insoluble in blood. Suitable biocompatible polymers include, by way of example, cellulose acetates7,10-11 (including cellulose diacetate9), ethylene vinyl alcohol copolymers8,12, hydrogels (e.g., acrylics), polyacrylonitrile, polyvinylacetate, cellulse acetate butyrate, nitrocellulose, copolymers of urethane/carbonate, copolymers of styrene/maleic acid, and mixtures thereof.13 Preferably, the biocompatible polymer does not induce chronic inflammation when employed in vivo.
The particular biocompatible polymer employed is not critical and is selected relative to the viscosity of the resulting polymer solution, the solubility of the biocompatible polymer in the biocompatible solvent, and the like. Such factors are well within the skill of the art.
Preferred biocompatible polymers include cellulose diacetate and ethylene vinyl alcohol copolymer. Cellulose diacetate polymers are either commercially available or can be prepared by art recognized procedures. In a preferred embodiment, the number average molecular weight, as determined by gel permeation chromatography, of the cellulose diacetate composition is from about 25,000 to about 100,000 more preferably from about 50,000 to about 75,000 and still more preferably from about 58,000 to 64,000. The weight average molecular weight of the cellulose diacetate composition, as determined by gel permeation chromatography, is preferably from about 50,000 to 200,000 and more preferably from about 100,000 to about 180,000. As is apparent to one skilled in the art, with all other factors being equal, cellulose diacetate polymers having a lower molecular weight will impart a lower viscosity to the composition as compared to higher molecular weight polymers. Accordingly, adjustment of the viscosity of the composition can be readily achieved by mere adjustment of the molecular weight of the polymer composition.
Ethylene vinyl alcohol copolymers comprise residues of both ethylene and vinyl alcohol monomers. Small amounts (e.g., less than 5 mole percent) of additional monomers can be included in the polymer structure or grafted thereon provided such additional monomers do not alter the sealing properties of the composition. Such additional monomers include, by way of example only, maleic anhydride, styrene, propylene, acrylic acid, vinyl acetate and the like.
Ethylene vinyl alcohol copolymers are either commercially available or can be prepared by art recognized procedures. Preferably, the ethylene vinyl alcohol copolymer composition is selected such that a solution of 6 weight percent of the ethylene vinyl alcohol copolymer, 35 weight percent of a tantalum contrast agent in DMSO has a viscosity equal to or less than 60 centipoise at 20xc2x0 C. As is apparent to one skilled in the art, with all other factors being equal, copolymers having a lower molecular weight will impart a lower viscosity to the composition as compared to higher molecular weight copolymers. Accordingly, adjustment of the viscosity of the composition as necessary for catheter delivery can be readily achieved by mere adjustment of the molecular weight of the copolymer composition.
As is also apparent, the ratio of ethylene to vinyl alcohol in the copolymer affects the overall hydrophobicity/hydrophilicity of the composition which, in turn, affects the relative water solubility/insolubility of the composition as well as the rate of precipitation of the copolymer in an aqueous solution (e.g., blood). In a particularly preferred embodiment, the copolymers employed herein comprise a mole percent of ethylene of from about 25 to about 60 and a mole percent of vinyl alcohol of from about 40 to about 75. These compositions provide for requisite precipitation rates suitable for use in sealing endoleaks arising from endovascular repair of an abdominal aortic aneurysm.
The term xe2x80x9ccontrast agentxe2x80x9d refers to a biocompatible (non-toxic) radiopaque material capable of being monitored during injection into a mammalian subject by, for example, radiography or fluoroscopy. The contrast agent can be either water soluble or water insoluble. Examples of water soluble contrast agents include metrizamide, iopamidol, iothalamate sodium, iodomide sodium, and meglumine.
The term xe2x80x9cwater insoluble contrast agentxe2x80x9d refers to a water insoluble (i.e., has a water solubility of less than 0.01 mg/ml at 20xc2x0 C.), radiopaque material capable of being monitored during injection into a mammalian subject by, for example, radiography or fluoroscopy. Examples of water insoluble contrast agents include tantalum, tantalum oxide and barium sulfate, which are commercially available in the proper form for in vivo use. Methods for preparing such water insoluble biocompatible contrast agents having an average particle size of about 10 xcexcm or less are described below. Other water insoluble contrast agents include gold, tungsten and platinum.
The term xe2x80x9cbiocompatible solventxe2x80x9d refers to an organic material liquid at least at body temperature of the mammal in which the biocompatible polymer is soluble and, in the amounts used, is substantially non-toxic. Suitable biocompatible solvents include, by way of example, ethanol, acetone, dimethylsulfoxide, analogues/homologues of dimethylsulfoxide, ethyl lactate, and the like. Aqueous mixtures with the biocompatible solvent can-also be employed provided that the amount of water employed is sufficiently small that the dissolved polymer precipitates upon-contact with-the blood. Preferably, the biocompatible solvent is dimethylsulfoxide (DMSO).
The term xe2x80x9cencapsulationxe2x80x9d as used relative to the contrast agent being encapsulated in the polymer precipitate is not meant to infer any physical entrapment of this agent within the precipitate much as a capsule encapsulates a medicament. Rather, this term is used to mean that an integral coherent precipitate forms which does not separate into individual components.
The term xe2x80x9cadheres toxe2x80x9d as used herein means that the composition formed in situ retains the position/location where the polymer mass formed after injection and thereby functions to seal the endoleak. This term does not necessarily infer that the composition acts as an adhesive although in the case of, for example, a cyanoacrylate prepolymer, the solid composition formed may, in fact, be adhesive.
The term xe2x80x9cbiocompatible prepolymerxe2x80x9d. refers to materials which polymerize in situ to form a polymer and which, in the amounts employed, are non-toxic, chemically inert, and substantially non-immunogenic, when used internally in the patient and which are substantially insoluble in blood. Suitable biocompatible prepolymers include, by way of example, cyanoacrylates14,15,16, hydroxyethyl methacrylate, silicone prepolymers, and the like. The prepolymer can either be a monomer or a reactive oligomer16. Preferably, the biocompatible prepolymer does not induce chronic inflammation when employed in vivo.
The compositions used in the methods of this invention are fluid compositions characterized by the fact that these compositions form a coherent mass in vivo which adheres to the vascular and/or prosthetic wall at the site of the endoleak thereby sealing the leak. The fluid compositions employed in the methods of this invention are polymer or prepolymer compositions prepared by conventional methods whereby each of the components is added and the resulting composition mixed or stirred together until the overall composition is substantially homogeneous.
In one embodiment, fluid polymer compositions preferably comprise a biocompatible polymer, a biocompatible solvent and optionally a contrast agent. Such compositions can be prepared by adding sufficient amounts of the biocompatible polymer to the biocompatible solvent to achieve the effective concentration for the polymer composition. Preferably, the polymer composition will comprise from about 2.5 to about 12.0 weight percent of the biocompatible polymer composition based on the total weight of the polymer composition and more preferably from about 4 to about 5.4 weight percent. If necessary, gentle heating and stirring can be used to effect dissolution of the biocompatible polymer into the biocompatible solvent, e.g., 12 hours at 50xc2x0 C.
When employed, sufficient amounts of the contrast agent are then added to the biocompatible polymer/solvent composition to achieve the effective concentration for the complete composition. Preferably, the composition will comprise from about 10 to about 40 weight percent of the contrast agent and more preferably from about 20 to about 40 weight percent and even more preferably about 30 weight percent. Insofar as the contrast agent may not be soluble in the biocompatible solvent (e.g., a water insoluble contrast agent), stirring is employed to effect homogeneity of the resulting suspension.
In order to enhance formation of the suspension, the particle size of the water insoluble contrast agent is preferably maintained at about 10 xcexcm or less and more preferably at from about 1 to about 5 xcexcm (e.g., an average size of about 2 xcexcm). In one preferred embodiment, the appropriate particle size of the contrast agent is prepared, for example, by fractionation. In such an embodiment, a water insoluble contrast agent such as tantalum having an average particle size of less than about 20 microns is added to an organic liquid such as ethanol (absolute) preferably in a clean environment. Agitation of the resulting suspension followed by settling for approximately 40 seconds permits the larger particles to settle faster. Removal of the upper portion of the organic liquid followed by separation of the liquid from the particles results in a reduction of the particle size which is confirmed under an optical microscope. The process is optionally repeated until a desired average particle size is reached.
When no contrast agent is employed, the biocompatible solvent is preferably employed at a concentration of from 88 to about 97.5 weight percent of the biocompatible polymer composition based on the total weight of the polymer composition and more preferably from about 90 to about 95 weight percent.
When a contrast agent is employed, the biocompatible solvent is preferably employed at a concentration of from 52 to 87.5 weight percent based on the total weight of the composition; more preferably from about 54.8 to about 76 weight percent; and even more preferably 64.8 to about 66 weight percent. Typical examples of suitable concentrations of individual components are given in the table below:
The particular order of addition of components to the biocompatible solvent is not critical and stirring of the resulting solution/suspension is conducted as necessary to achieve homogeneity of the composition. Preferably, mixing/stirring of the composition is conducted under an anhydrous atmosphere at ambient pressure. The resulting composition is heat sterilized and then stored preferably in sealed amber bottles or vials until needed.
Each of the polymers recited herein is commercially available but can also be prepared by methods well known in the art. For example, polymers are typically prepared by conventional techniques such as radical, thermal, UV, xcex3 irradiation, or electron beam induced polymerization employing, as necessary, a polymerization catalyst or polymerization initiator to provide for the polymer composition. The specific manner of polymerization is not critical and the polymerization techniques employed do not form a part of this invention.
In order to maintain solubility in the biocompatible solvent, the polymers described herein are preferably not cross-linked.
In another embodiment, the fluid compositions comprise prepolymer compositions which preferably comprise a biocompatible prepolymer and a water insoluble contrast agent. Such compositions can be prepared by adding sufficient amounts of the contrast agent to the solution (e.g., liquid prepolymer) to achieve the effective concentration for the complete composition. Preferably, the prepolymer composition will comprise from about 10 to about 40 weight percent of the contrast agent and more preferably from about 20 to about 40 weight percent and even more preferably about 30 weight percent. The water insoluble contrast agent is typically not soluble in the biocompatible prepolymer composition and stirring is employed to effect homogeneity of the resulting suspension. In order to enhance formation of the suspension, the particle size of the contrast agent is preferably maintained at about 10 xcexcm or less and more preferably at from about 1 to about 5 xcexcm (e.g., an average size of about 2 xcexcm).
When the prepolymer is liquid, the use of a biocompatible solvent is not absolutely necessary but may be preferred to provide for an appropriate viscosity, etc. in the composition. Preferably, when employed, the biocompatible solvent will comprise from about 30 to about 90 weight percent of the biocompatible prepolymer composition based on the total weight of the prepolymer composition and more preferably from about 60 to about 80 weight percent. When a biocompatible solvent is employed, the prepolymeric composition typically comprises from about 10 to about 50 weight percent of the prepolymer based on the total weight of the composition. Typical examples of suitable concentrations of individual components are given in the table below:
In a particularly preferred embodiment, the prepolymer is a cyanoacrylate ester which is preferably employed in the absence of a biocompatible solvent. When so employed, the cyanoacrylate composition is selected to have a viscosity of from about 5 to about 20 centipoise at 20xc2x0 C.
The particular order of addition of components is not critical and stirring of the resulting suspension is conducted as necessary to achieve homogeneity of the composition. Preferably, mixing/stirring of the composition is conducted under an anhydrous atmosphere at ambient pressure. The resulting composition is sterilized and then stored preferably in sealed amber bottles or vials until needed.
The compositions described above can then be employed in methods for the catheter assisted sealing of endoleaks formed by endovascular repair of an abdominal aortic aneurysm by an endovascular prosthesis.
Specifically, endovascular repair of such aneurysms involves the introduction of an endovascular prosthesis into the abdominal aortic aneurysm which is an art recognized procedure described, for example, by Parodi.17 This procedure typically consists of dissection of the femoral artery at the groin and introduction of an endovascular prosthesis inside the abdominal aortic aneurysm. Upon insertion, the prosthesis excludes the aneurysm sac from the systemic vascular circulation thereby repairing the aneurysm. Suitable endovascular prostheses for endovascular repair of abdominal aortic aneurysms are well known in the art and are described, for example, by Beebe, et al.5 Such prostheses, by themselves, do not form part of this invention. Similarly, catheters for delivering such endovascular prostheses to the site of the abdominal aortic aneurysm are also well known in the art and are commercially available. Such catheters, by themselves, also do not form part of this invention.
In any event, in the methods of this invention, a sufficient amount of the fluid composition described above is introduced at the site of the endoleak via a catheter or needle delivery means preferably under fluoroscopy so that sealing of the endoleak can be visualized. The specific amount of fluid composition employed is dictated by the total size of the endoleak, whether penetration of the fluid composition into the aneurysm is desirable and/or achievable and other factors such as the concentration of polymer/prepolymer in the composition, the rate of solids formation, etc. Such factors are well within the skill of the art.
Prior to sealing the endoleak in the manner described above, the clinician would first identify the site or sites of the endoleak which typically include the interface of the aortic wall to the end of the endovascular prosthesis; defects within the endovascular prosthesis such as at juncture points between segments of the prosthesis which permit blood flow through the prosthesis itself; and retrograde flow from patent lumbar and inferior mesenteric arteries following placement of the endovascular prosthesis in the aorta.
Access to these sites of endoleaks can be achieved by microcatheter retrograde access via the patent lumbar and/or inferior mesenteric arteries or by endovascular methods or percutaneous puncture at the site of the endoleak. After access is achieved, delivery of the fluid composition proceeds as described above.
One particularly preferred method for catheter delivering the compositions described in the methods of this invention to the site of the endoleak is via a small diameter medical catheter. The particular catheter employed is not critical provided that polymeric catheter components are compatible with the fluid composition (i.e., the catheter components will not readily degrade in the fluid composition). In this regard, it is preferred to use polyethylene in the catheter components because of its inertness in the presence of the fluid composition described herein. Other materials compatible with the fluid compositions can be readily determined by the skilled artisan and include, for example, other polyolefins, fluoropolymers (e.g., Teflon(trademark)), silicone, etc.
Another particularly preferred method for the catheter injection of the polymer composition of this invention is described by Greff, et al., U.S. Pat. No. 5,830,178 which issued on Nov. 3, 1998 and which is incorporated herein by reference in its entirety.
When a fluid composition comprising a biocompatible polymer is introduced at the site of the endoleak, the biocompatible solvent diffuses rapidly into the blood and a solid coherent mass forms in situ which precipitate is the water insoluble polymer with any contrast agent encapsulated therein. Without being limited to any theory, it is believed that initially, a soft gel to spongy solid precipitate forms upon contact with the blood which mass adheres to the vascular or prosthetic wall thereby sealing the endoleak.
When a fluid composition comprising a biocompatible prepolymer is introduced at the site of the endoleak, the prepolymer polymerizes in situ to form a solid coherent mass or film with any water insoluble contrast agent encapsulated therein. This mass adheres to the vascular and/or prosthetic wall thereby sealing the endoleak.
When a contrast agent is employed in the fluid composition, sealing of the endoleak by this composition can be confirmed by injection of an independent contrast agent such iopamidol (50:50 mixture with saline) into the blood flow of the aorta. Failure of this contrast agent to reach the aneurysm sac as visualized by fluoroscopy confirms sealing of the endoleak.
The sealing of endoleaks can be conducted during the surgical repair of the abdominal aortic aneurysm or in a separate surgical procedure conducted subsequent to the surgical repair. All that is required is the determination of the location of the endoleaks in the patient and introduction of the fluid composition to seal such endoleaks.
The methods of this invention are preferably conducted by using kits of parts comprising two or more of the components necessary to effect the endoleak repair protocol. For example, in one embodiment, this kit comprises the following components:
(a) a fluid composition comprising a composition selected from the group consisting of (i) a biocompatible polymer and a biocompatible solvent and (ii) a biocompatible prepolymer and a water insoluble contrast agent which fluid composition forms a coherent mass in the presence of blood which mass adheres to the vascular surface and/or the surface of the endovascular prosthesis;
(b) a catheter suitable for delivering the fluid composition to an endoleak site formed from endovascular repair of an aneurysm; and
(c) a catheter suitable for delivering an endovascular prosthesis to the aneurysm.
In a preferred embodiment, this kit further comprises an endovascular prosthesis.
In another embodiment, this kit comprises the following components:
(a) a fluid composition comprising a composition selected from the group consisting of (i) a biocompatible polymer and a biocompatible solvent and (ii) a biocompatible prepolymer and a water insoluble contrast agent which fluid composition forms a coherent mass in the presence of blood which mass adheres to the vascular surface and/or the surface of the endovascular prosthesis;
(b) a catheter suitable for delivering the fluid composition to an endoleak site formed from endovascular repair of an aneurysm; and
(c) an endovascular prosthesis.
In a preferred embodiment, this kit further comprises a catheter suitable for delivering an endovascular prosthesis to the aneurysm.
The methods described herein are useful in reducing or eliminating blood flow through an endoleak into an endovascularly repaired aneurysm thereby reducing or eliminating the possible rupture of the aneurysm. Accordingly, these methods find use in human and other mammalian subjects requiring closure of such endoleaks. Additionally, when a water insoluble contrast agent is employed, the stability of the closure can be monitored weeks, months or even years after sealing by non-invasive fluoroscopic techniques. Resealing of the endoleak is also facilitated by the presence of the water insoluble contrast agent which permits the clinician to readily identify the site of treated endoleaks.
It is contemplated that the procedures set forth above can be employed for sealing endoleaks arising from insertion of an endovascular prosthesis at vascular sites other than the abdominal aorta. Such prostheses could be used to repair aneurysms and other vascular diseases at vascular sites such as peripheral vessels.